While listing the requirements of a pastor in Titus 1, Paul says a pastor “must hold firmly to the trustworthy message as it has been taught, so that he can encourage others by sound doctrine and refute those who oppose it.”[1] In other words, one of the requirements for being a pastor is understanding theology well enough to be able to use it in a church. St. Irenaeus of Lyons was one pastor from church history who carried out this call.

During Irenaeus’s time, the main theological threat to Christianity was the ancient heresy of Gnosticism. If you listen closely, you can hear early rumblings of Gnostic thought in some of the New Testament books, especially 1 John. John goes out of his way to make sure that everyone knows that Jesus was a physical human being, which the Gnostics denied. By the time that Irenaeus became a church leader, Gnosticism had grown to a full-fledged heresy that threatened the unity and holiness of the Church.

Unfortunately for Christians, Gnosticism was (and is) notoriously difficult to understand. To offer a substantive rebuttal was a demanding task indeed. Irenaeus didn’t shrink from this task, however. At the beginning of his long, sometimes inscrutable work, Against Heresies, Irenaeus tells us his purpose for doing so much work for his fellow believers. “Lest… through my neglect, some should be carried off, even as sheep are by wolves, while they perceive not the true character of these men,—because they outwardly are covered with sheep’s clothing…, and because their language resembles ours, while their sentiments are very different,—I have deemed it my duty… to unfold to thee, my friend, these portentous and profound mysteries, which do not fall within the range of every intellect… I do this, in order that, thou… mayest… exhort [other Christians] to avoid such an abyss of madness and blasphemy against Christ.”[2]

That’s an impressive passage for several reasons, not least of which is the grammar involved in such a long sentence! Irenaeus knew that the Gnostic heresy was hurting the average Christian: the Gnostics sounded like Christians when they taught, but their ideas were antithetical to biblical Christianity. Irenaeus did the hard, intellectual work of understanding the inscrutably complex doctrines of the Gnostics so that he could tell his brothers and sisters in Christ that the Gnostic doctrines would lead them away from Christ’s Church. In short, Irenaeus was a pastor-theologian par excellence.

Obviously, not every pastor is able or called to be a theologian on Irenaeus’s level. Few of us need to write a book as long and complex as Against Heresies. But, all pastors are called to cling to good doctrine and to use doctrine to guide their church. Differences to the side, Irenaeus is a good model for us: He faced the challenges that were hurting Christians head-on even though it was a difficult task. In the 21st century, we need pastors who meet the unique theological problems of our culture head-on even when it’s hard.